The Evolution of Human Birth

The Evolution of
Human Birth
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Date
Monkey’s are born facing the same direction of
their mother.
If humans tried to guide their babies out the way monkey’s
do, they risks bending its back awkwardly against the
natural curve of its spine.
Pulling on a newborn at this angle risks injury to its spinal
cord, nerves and muscles.
What is the history of the conflict
between maternal pelvis and fetal
head size prior to the last 150 years?
Human birth was constrained by the need to pass a
head that was enlarging over geologic time through
a pelvis that was being extensively modified by the
requirement for bipedality, such that cephalopelvic
disproportion is not an uncommon cause of both
maternal and fetal death today where Cesarean
sections are not readily available.
*Human modifications for childbirth include a
somewhat flexible cranium due to unfused skull
bones in the newborn and maternal pelvis
flexibility due to symphyseal ligament relaxation.
*The most significant modification in
humans compared to other extant
primates is altricial birth, which is
the birth of helpless newborns
As you can see, the pelvic bone of
the Neanderthal’s was relatively
larger than that of modern humans.
The same can be said for this photo of
the Australopithecus bones.
So, what are you taking away from this?
*Women today give birth with the help of doctor’s but used to do it
on their own.
* Women’s physical pelvic bone shape has changed over time,
making it more difficult to deliver a baby.
Works Cited
Rosenberg, K., & Trevathan, W. (2012). Evolution of human
birth. Scientific American, 80-84.
http://ezproxy.gavilan.edu/loggedin/evolution_
human_birth.pdf
Walsh, J. A. (2008). Evolution & the cesarean section
rate. American Biology Teacher (National
Association Of Biology Teachers), 70(7), 401404.
Weaver, T. D., & Hublin, J. (2009). Neandertal birth canal
shape and the evolution of human childbirth.
Proceedings Of The National Academy Of
Sciences Of The United States Of America,
106(20), 8151-8156.
doi:10.1073/pnas.0812554106